Even though you chose to use the word most, the topic itself suggest otherwise. So am to begin by correcting your statement in the narration of this topic. Not all attacks, be it suicide or killings, are carried out by Muslims. Attacks of this nature has been going on long before it's constant association with Muslims.
How many Muslims do you personally know? Now, tell me how many of those Muslims you know behave or act violently always? I guess you have your answer now, but am still going to speak further in order to make my point clear.
The Oxford dictionary defines terrorism as the unlawful use of violence, especially against civilians, in the pursuit of political aims. The word terrorist and terrorism was originated during the French revolution in the 18th century. If we were to go by this definition, do you honestly believe that violence of this nature hasn't been going on way past 18th century times? Then why do other attacks carried out by non-muslims never get to be called terrorism? This is because the word terrorism gained mainstream recognition after American President Ronald Reagan used it to refer to a 1983 bombings in Beirut carried out by a group of angry Muslims, and also President George Bush after september 11 world trade center bombings. Ever since, it's become a norm. Every attack on civilians carried out by a Muslim automatically becomes terrorism. I guess this is the reason why most non-Muslim think Islam is violent religion.
Islam is no different from Christianity in a religious manner. In fact, the major difference between Christianity and Islam is their method of prayer and the belief of Prophet Muhammad, which Christians do not believe in, and Jesus Christ the Almighty father, which Muslims believe him to be the prophet of God and not the father, son or holy spirit. Asides all these, almost every other thing in both religions are the same. The bible and Qur'an have the same gospels and historically stories in common. So, I don't see why people should think Islam preaches violence. Islamic books have writing translations in English just like the bible, you can easily get one and see the contents for yourself.
Hence, I'll like to add that violence has and will always be a part of man's nature. History has shown us many brutal wars waged on men against themselves. Even the general values and cultures, relationships between nations and freedom to stroll around the world were all built on blood, blood of many innocence. The attacks we refer to terrorism has been around for as long as history can tell us. It's just unfortunate that most talked about attacks are those carried out by misguided Muslims, while other attacks by non-muslim are either ignored or don't make headlines as terrorism.